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Our application concerns the automated detection of vessels in retinal images to improve understanding of the disease mechanism, diagnosis and treatment of retinal and a number of systemic diseases. We propose a new framework for segmenting retinal vasculatures with much improved accuracy and efficiency. The proposed framework consists of three technical components: Retinex-based image inhomogeneity correction, local phase-based vessel enhancement and graph cut-based active contour segmentation. These procedures are applied in the following order. Underpinned by the Retinex theory, the inhomogeneity correction step aims to address challenges presented by the image intensity inhomogeneities, and the relatively low contrast of thin vessels compared to the background. The local phase enhancement technique is employed to enhance vessels for its superiority in preserving the vessel edges. The graph cut-based active contour method is used for its efficiency and effectiveness in segmenting the vessels from the enhanced images using the local phase filter. We have demonstrated its performance by applying it to four public retinal image datasets (3 datasets of color fundus photography and 1 of fluorescein angiography). Statistical analysis demonstrates that each component of the framework can provide the level of performance expected. The proposed framework is compared with widely used unsupervised and supervised methods, showing that the overall framework outperforms its competitors. For example, the achieved sensitivity (0:744), specificity (0:978) and accuracy (0:953) for the DRIVE dataset are very close to those of the manual annotations obtained by the second observer.

Bevacizumab has been suggested to have similar effectiveness to ranibizumab for treatment of neovascular age-related macular degeneration. The Inhibition of VEGF in Age-related choroidal Neovascularisation (IVAN) trial was designed to compare these drugs and different regimens. Here, we report the findings at the prespecified 2-year timepoint. In a multicentre, 2×2 factorial, non-inferiority randomised trial, we enrolled adults aged at least 50 years with active, previously untreated neovascular age-related macular degeneration and a best corrected distance visual acuity (BCVA) of at least 25 letters from 23 hospitals in the UK. Participants were randomly assigned (1:1:1:1) to intravitreal injections of ranibizumab (0·5 mg) or bevacizumab (1·25 mg) in continuous (every month) or discontinuous (as needed) regimens, with monthly review. Study participants and clinical assessors were masked to drug allocation. Allocation to continuous or discontinuous treatment was masked up to 3 months, at which point investigators and participants were unmasked. The primary outcome was BCVA at 2 years, with a prespecified non-inferiority limit of 3·5 letters. The primary safety outcome was arterial thrombotic event or hospital admission for heart failure. Analyses were by modified intention to treat. This trial is registered, number ISRCTN92166560. Between March 27, 2008, and Oct 15, 2010, 628 patients underwent randomisation. 18 were withdrawn; 610 received study drugs (314 ranibizumab; 296 bevacizumab) and were included in analyses. 525 participants reached the visit at 2 years: 134 ranibizumab in continuous regimen, 137 ranibizumab in discontinuous regimen, 127 bevacizumab in continuous regimen, and 127 bevacizumab in discontinuous regimen. For BCVA, bevacizumab was neither non-inferior nor inferior to ranibizumab (mean difference −1·37 letters, 95% CI −3·75 to 1·01; p=0·26). Discontinuous treatment was neither non-inferior nor inferior to continuous treatment (−1·63 letters, −4·01 to 0·75; p=0·18). Frequency of arterial thrombotic events or hospital admission for heart failure did not differ between groups given ranibizumab (20 [6%] of 314 participants) and bevacizumab (12 [4%] of 296; odds ratio [OR] 1·69, 95% CI 0·80–3·57; p=0·16), or those given continuous (12 [4%] of 308) and discontinuous treatment (20 [7%] of 302; 0·56, 0·27–1·19; p=0·13). Mortality was lower with continuous than discontinuous treatment (OR 0·47, 95% CI 0·22–1·03; p=0·05), but did not differ by drug group (0·96, 0·46–2·02; p=0·91). Ranibizumab and bevacizumab have similar efficacy. Reduction in the frequency of retreatment resulted in a small loss of efficacy irrespective of drug. Safety was worse when treatment was administered discontinuously. These findings highlight that the choice of anti-VEGF treatment strategy is less straightforward than previously thought. UK National Institute for Health Research Health Technology Assessment programme.

Previous work has identified that malarial retinopathy has diagnostic value in paediatric cerebral malaria (CM). To improve our understanding of malarial retinopathy as a predictor of cerebral parasite sequestration in paediatric CM we reviewed data from the Blantyre autopsy study, to test the hypothesis that malarial retinopathy is an accurate predictor of cerebral parasite sequestration in an autopsy cohort. We performed a retrospective analysis of data collected from a consecutive series of patients presenting to the Pediatric Research Ward at Queen Elizabeth Central Hospital in Blantyre, Malawi between 1996 and 2010. We determined the diagnostic accuracy of malarial retinopathy as a predictor of cerebral parasite sequestration in a cohort of children with fatal CM. Of 84 children included in the study, 65 met the World Health Organization clinical diagnostic criteria for CM during life. Eighteen (28%) of 65 did not have evidence of cerebral parasite sequestration at autopsy and 17 had an alternative cause of death. Malarial retinopathy had a sensitivity of 89.4% (95% CI [77.6%, 95.6%]) and specificity of 73.0% (95% CI [57.2%, 84.8%]) to predict cerebral parasite sequestration. In a subset of patients with graded retinal assessments, this was improved to 94.3% (95% CI [81.7%, 98.7%]) and 88.0% (95% CI [70.4%, 96.2%]) by reclassifying patients in whom the only retinal sign was 1-5 haemorrhages in a single eye as retinopathy negative. This study is limited by its retrospective nature and the inherent selection bias associated with autopsy studies. Malarial retinopathy remains the most specific point-of-care test for CM in endemic areas. Its specificity may be improved, without sacrificing sensitivity, by reclassifying patients in whom the only retinal sign is fewer than 5 haemorrhages in a single eye as malarial retinopathy negative. A management algorithm is proposed for integration of malarial retinopathy into clinical care in both well-resourced and resource-limited environments.

Background Diabetic retinal neurodegeneration (DRN) is increasingly recognised as an early and progressive neuronal dysfunction. Despite emerging therapeutic approaches, there are no standardised biomarkers. We aim to investigate functional and structural biomarkers of DRN in people with diabetes (PWD) with no or early diabetic retinopathy (DR). Methods Functional measures included handheld radial shape discrimination (hRSD), near and distant visual acuity (VA). Structural changes were evaluated using optical coherence tomography (OCT)-derived retinal thicknesses (Early Treatment Diabetic Retinopathy Study (ETDRS) subfields). Mean thicknesses of the inner and outer ETDRS subfields were averaged to derive inner and outer ring estimates. Pearson’s correlation assessed associations between normally distributed variables. Group differences were analysed using Student’s t-test for continuous data, Chi-squared or Fisher’s exact tests for categorical variables, and one-way ANOVA with Bonferroni-adjusted post hoc tests for multiple groups. Results The study included a single eye from 50 healthy participants (HP; Group 1, 55 ± 14y), 26 PWD with no DR (Group 2, 55 ± 14y), and 46 with early DR (Group 3, 57 ± 17y). hRSD and VA were worse in Groups 1 to 3 (all p  < 0.001). Worse function (measured via hRSD) was associated with inner retinal thinning ( p  < 0.05). Compared to HP, PWD (Groups 2 and 3) showed thinning of the total retina (most subfields), retinal nerve fibre layer (RNFL; outer ETDRS ring), ganglion cell layer (GCL) and inner plexiform layer (IPL) in the inner ring, and outer nuclear layer (ONL) in the central subfield (CSF) ( p  < 0.05). Group 3 also showed GCL and IPL thinning (outer ring) ( p  < 0.05). In 23 PWD followed over 205 ± 109 days, GCL, IPL, and inner nuclear layer (INL) thicknesses decreased ( p  < 0.05). Conclusions Functional and structural changes occur early in DR. hRSD and retinal thicknesses are promising biomarkers for DRN. Longitudinal data suggest DRN to be progressive. Clinical trial number Not applicable.

Aims Neurodegeneration and glial activation are primary events in the pathogenesis of diabetic retinopathy. Serum glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) are biomarkers of underlying neuroinflammatory and neurodegenerative disease processes. The aim of the present study was to assess the usefulness of these serum biomarkers for the identification and monitoring of retinal neurodysfunction in subjects with type 2 diabetes. Methods A case–control study was designed including 38 patients from the placebo arm of the EUROCONDOR clinical trial: 19 with and 19 without retinal neurodysfunction assessed by multifocal electroretinography. GFAP and NfL were measured by Simoa. Results Serum levels of GFAP and NfL directly correlated with age ( r  = 0.37, p  = 0.023 and r  = 0.54, p  < 0.001, respectively). In addition, a direct correlation between GFAP and NfL was observed ( r  = 0.495, p  = 0.002). Serum levels of GFAP were significantly higher at baseline in those subjects in whom neurodysfunction progressed after the 2 years of follow-up (139.1 ± 52.5 pg/mL vs. 100.2 ± 54.6 pg/mL; p  = 0.04). Conclusions GFAP could be a useful serum biomarker for retinal neurodysfunction. Monitoring retinal neurodysfunction using blood samples would be of benefit in clinical decision-making. However, further research is needed to validate this result as well as to establish the best cutoff values.

We investigated the performance of the handheld radial shape discrimination (hRSD) test in detecting the development of neovascular AMD (nAMD) in a prospective, longitudinal, observational study. Patients diagnosed with unilateral nAMD, with no nAMD in the other eye (the study eye, SE), completed the hRSD test on consecutive, routine clinic visits up to a maximum of 12, or until they were diagnosed with nAMD in the SE based on slit-lamp biomicroscopy and spectral-domain OCT assessment, with fluorescein angiography confirmation. Masked grading was carried out to confirm the diagnosis of nAMD, and to ensure no cases of nAMD were missed. Receiver operating characteristics (ROC) analysis was used to explore the diagnostic performance of the hRSD test relative to clinical diagnosis. Data were available from 179 patients of whom 19 (10.6%; \"converters\") developed nAMD in the SE. The mean hRSD threshold at conversion was -0.47 (95% CI -0.38 to -0.55) logMAR compared to -0.53 (-0.50 to -0.57) logMAR in 160 non-converters. hRSD threshold in the converters began to decline 190 days before diagnosis of nAMD. The ROC curve demonstrated that at an hRSD cut-off of -0.60 logMAR, sensitivity was 0.79 (0.54-0.94) with a specificity of 0.54 (0.46-0.62); positive and negative predictive values were 0.16 and 0.96 respectively. We conclude that the hRSD test has moderate sensitivity for detecting the earliest stages of nAMD in the at-risk fellow eyes of patients with unilateral nAMD, compared to clinical diagnosis. Given its relative inexpensiveness, ease of use and the inherent connectivity of the platforms it can be presented on, it may have a role in early detection of nAMD in the population at large.

The detection and assessment of leakage in retinal fluorescein angiogram images is important for the management of a wide range of retinal diseases. We have developed a framework that can automatically detect three types of leakage (large focal, punctate focal and vessel segment leakage) and validated it on images from patients with malarial retinopathy. This framework comprises three steps: vessel segmentation, saliency feature generation and leakage detection. We tested the effectiveness of this framework by applying it to images from 20 patients with large focal leak, 10 patients with punctate focal leak and 5,846 vessel segments from 10 patients with vessel leakage. The sensitivity in detecting large focal, punctate focal and vessel segment leakage are 95%, 82% and 81%, respectively, when compared to manual annotation by expert human observers. Our framework has the potential to become a powerful new tool for studying malarial retinopathy and other conditions involving retinal leakage.

Background. In patients with cerebral malaria (CM), retinal angiography allows the study of infected central nervous system microvasculature in vivo. We aimed to examine retinal perfusion in children with CM by use of fluorescein angiography to investigate the pathophysiology of CM. Methods. We performed fluorescein angiography on children with CM admitted to Queen Elizabeth Central Hospital, Malawi. We related angiograms to funduscopic findings. Results. Fluorescein angiography was performed for 34 patients with CM, and impaired perfusion was identified in 28 (82%). Areas of capillary nonperfusion (CNP) were seen in 26 patients (76%). Multiple, scattered areas of CNP were typical and topographically matched to retinal whitening. Larger retinal vessels were occluded in 9 patients (26%) who had associated ischemia. These vessels appeared white on ophthalmoscopy. Intravascular abnormalities were seen in 9 patients (26%), including filling defects and mottling of the blood column. Limited fluorescein leakage occurred in 15 patients (44%) and was not related to angiographic intravascular abnormalities or visible vessel discoloration. Conclusions. Impaired perfusion occurs in the retinal microvasculature of most children with CM. This is evidence for hypoxia and ischemia as important components in the pathogenesis of CM. Vessel occlusion and filling defects are likely to be due to sequestration of infected erythrocytes. Interventions which improve perfusion or limit hypoxic injury may be beneficial in CM.

Capillary non-perfusion (CNP) in the retina is a characteristic feature used in the management of a wide range of retinal diseases. There is no well-established computation tool for assessing the extent of CNP. We propose a novel texture segmentation framework to address this problem. This framework comprises three major steps: pre-processing, unsupervised total variation texture segmentation, and supervised segmentation. It employs a state-of-the-art multiphase total variation texture segmentation model which is enhanced by new kernel based region terms. The model can be applied to texture and intensity-based multiphase problems. A supervised segmentation step allows the framework to take expert knowledge into account, an AdaBoost classifier with weighted cost coefficient is chosen to tackle imbalanced data classification problems. To demonstrate its effectiveness, we applied this framework to 48 images from malarial retinopathy and 10 images from ischemic diabetic maculopathy. The performance of segmentation is satisfactory when compared to a reference standard of manual delineations: accuracy, sensitivity and specificity are 89.0%, 73.0%, and 90.8% respectively for the malarial retinopathy dataset and 80.8%, 70.6%, and 82.1% respectively for the diabetic maculopathy dataset. In terms of region-wise analysis, this method achieved an accuracy of 76.3% (45 out of 59 regions) for the malarial retinopathy dataset and 73.9% (17 out of 26 regions) for the diabetic maculopathy dataset. This comprehensive segmentation framework can quantify capillary non-perfusion in retinopathy from two distinct etiologies, and has the potential to be adopted for wider applications.

To investigate the economic impact of introducing targeted screening and laser photocoagulation treatment for sight-threatening diabetic retinopathy and macular edema in a setting with no previous screening or laser treatment for diabetic retinopathy in sub-Saharan Africa. A cohort Markov model was built to compare combined targeted screening and laser treatment for patients with sight-threatening diabetic retinopathy and macular edema against no intervention. Primary outcomes were incremental cost per quality-adjusted life year (QALY) gained and per disability-adjusted life year (DALY) averted. Primary data were collected on 357 participants from the Malawi Diabetic Retinopathy Study, a prospective, observational cohort study. Multiple scenarios were explored and a probabilistic sensitivity analysis was performed. In the base case (age: 50 years, service utilization rate: 80%), the cost of the intervention and the years of severe visual impairment averted per patient screened were $209 and 2.2 years respectively. Applying the World Health Organization threshold of cost-effectiveness for Malawi ($679), the base case was cost-effective when QALYs were used ($400 per QALY gained) but not when DALYs were used ($766 per DALY averted). The intervention was more cost-effective when it targeted younger patients (age: 30 years) and less cost-effective when the utilization rate was lowered to 50%. Annual photographic screening of diabetic patients attending medical diabetes clinics in Malawi, with the provision of laser treatment for those with sight-threatening diabetic retinopathy and macular edema, appears to be cost-effective in terms of QALYs gained, in our base case scenario. Cost-effectiveness improves if services are utilized more intensively and extended to younger patients.